Carbon monoxide shutoff system for electric generator

ABSTRACT

A carbon monoxide shutoff system for an engine of a portable electrical generator has a carbon monoxide gas sensor, a microcontroller, and an output indicator. The carbon monoxide gas sensor generates an output electrical current proportional to a detected concentration of ambient carbon monoxide. The microcontroller has an input connected to the carbon monoxide gas sensor, and an output connected to an operational control of the engine. A deactivation signal generated by the microcontroller in response to detection of a deactivation condition is based upon the output electrical current from the carbon monoxide gas sensor matching predefined value and duration thresholds. The deactivation signal is operative to stop the engine.

CROSS-REFERENCE TO RELATED APPLICATIONS

The application relates to and claims the benefit under 35 U.S.C. §119(e) to U.S. Provisional Patent Application No. 62/711,329 filed Jul.27, 2018 and entitled “CARBON MONOXIDE SHUTOFF SYSTEM FOR ELECTRICGENERATOR” the entire contents of which is wholly incorporated byreference herein.

STATEMENT RE: FEDERALLY SPONSORED RESEARCH/DEVELOPMENT

Not Applicable

BACKGROUND 1. Technical Field

The present disclosure relates generally to electric generators andsafety devices therefor, and more particularly, to a carbon monoxideshutoff system for electric generators.

2. Related Art

Electrical generators are used to convert mechanical energy intoelectrical energy. There are innumerable configurations and sizes ofelectrical generators that find application in various contexts. Theseinclude powering national, regional, and local electrical grids,providing backup or secondary power to a specific location or buildingin case of a fault in the electrical grid, as well as serving as aprimary power source at locations where transmission lines from anelectric utility have not yet been extended, or where there is only atemporary need for electrical power.

Depending on the application, a generator may use different mechanicalsources and are therefore configured with particular devices thatgenerate and/or harness mechanical energy, such as steam, gas, or waterturbines, or internal combustion engines. The mechanical energy as it isoutput from these devices is typically a rotational motion or a linearreciprocal motion, and is converted to electrical energy with dynamos(for DC power) or alternators (for AC power).

Specifically, dynamos or alternators include an armature, which is acoil or a series of conductive windings that are placed in proximity toa magnet. The armature is mechanically moved about the magnet, therebygenerating an electromotive force that drives an armature electricalcurrent. This electrical current is relayed to the various electricdevices connected to the generator.

A portable generator is useful where power generation requirements areat the individual or group level, as electrical power can be immediatelyavailable in locations that are otherwise lacking in service from acentral utility. For example, new construction sites require electricityto power tools utilized in the construction activity, but it is notalways the case that the electrical utility has constructed power linesthereto. Portable generators may be brought to the construction site toprovide the needed electricity. In another example, portable generatorsmay be used to provide electrical power to run household appliances suchas refrigerators, microwave ovens, as well as lighting while camping inremote wilderness locations that have no power connections. Portablegenerators are also frequently purchased for home use to provide backuppower during an emergency where electrical power from the centralutility is intermittent or unavailable altogether.

In a typical configuration, the portable generator incorporates theaforementioned mechanical energy source and the electromagneticgenerators, e.g., the dynamo or the alternator, in a single standaloneunit. The mechanical energy source, as noted above, may be an internalcombustion engine that is powered by fuel such as gasoline, diesel,propane, and natural gas. The storage for such fuel is also incorporatedinto the portable generator, along with various fuel delivery and enginecontrol components. The engine may also be equipped with exhaust systemsthat limit noise and emissions, as well as cooling and internallubrication systems.

The frequency and shape of an alternating current signal output by thegenerator may vary depending on the operation of the engine, so agovernor that regulates its speed may be utilized. Alternatively, thedirectly generated alternating current signal may be filtered andrectified into a direct current (DC) voltage, and converted back to aconsistently shaped and timed alternating current (AC) signal with apower inverter. The operational details of the portable generator istypically reported by onboard indicators such as voltmeters, ammeters,fuel low indicators, oil low indicators, generated frequency, andtimers/counters.

Portable generators, like all fuel-burning appliances, generate exhaustgasses. Although specific composition ratios vary, exhaust gasses fromthe combustion of fuel and air in gasoline, diesel, and other internalcombustion engines include nitrogen, carbon dioxide, oxygen, nitrogenoxides, carbon monoxide, hydrocarbons, and sulfur dioxide, as well asother harmful particulate matter. One of the most harmful exhaust gassesis carbon monoxide, which is an invisible, odorless, colorless, andnon-irritant gas that is generated from the incomplete combustion offuel that prevents complete oxidation to carbon dioxide.

An exposure to high concentrations of carbon monoxide can result in theloss of consciousness, seizures, arrhythmias, and even death. Short ofdeath or loss of consciousness, those with acute carbon monoxidepoisoning from exposure to lower concentrations of carbon monoxide mayexperience a variety of symptoms such as headaches, dizziness, weakness,chest pains, and the like. It is understood that carbon monoxidecombines with the hemoglobin of the blood to form carboxyhemoglobin,which prevents it from carrying oxygen throughout the circulation systemof the body.

The operation of portable generators within enclosed or semi-enclosedspaces is one of the most common causes for carbon monoxide poisoning.During wintertime in locales where snowfall occurs, the consequent poweroutages necessitate the use of portable generators. Although numerouswarnings not to operate portable generators within the home, garage, orother enclosed space with adequate ventilation accompany the products,environmental conditions may not be conducive to safer operation. Forexample, ongoing rain or snow, or accumulated snow may make it difficultto run the portable generator outside the enclosed spaces of the home orgarage.

Portable generators are not the only source of carbon monoxide emissionsin a typical household, as cooking equipment, heating appliances such asfurnaces, space heaters, and fireplaces, as well as motor vehicles alloutput carbon monoxide. Various approaches have been taken to minimizethe possibility of carbon monoxide poisoning, one of the most prevalentbeing carbon monoxide alarms installed throughout an interior space. Awide range of sensing technologies are known in the art, includingoptochemical detectors that generate an alarm based upon the color of achemical pad changing in response to carbon monoxide exposure,electrochemical sensors that generate an alarm based upon an electricalsignal that relates to concentration levels of carbon monoxide, as wellas semiconductor sensors that generate an alarm based upon electricalcircuit parameters (e.g., resistance) that changes with exposure tocarbon monoxide. Beyond visual and audible alarms that are activatedwhen unsafe levels of carbon monoxide are detected within an atmosphere,affirmative actions may be initiated, such as the activation of aircirculation fans, opening doors/windows within the enclosed space,shutting down the equipment generating the carbon monoxide, and soforth.

Although there are several known systems for stopping the operation of aportable generator where high concentrations of carbon monoxide arepresent at the engine exhaust and areas proximate thereto, therecontinues to be a need for improved shutoff devices.

BRIEF SUMMARY

The present disclosure is directed to a carbon monoxide sensing modulethat shuts down a portable generator when a carbon monoxideconcentration above certain preset levels is detected.

One embodiment is a carbon monoxide shutoff system for an engine of aportable electrical generator that is generally comprised of a carbonmonoxide gas sensor, a microcontroller, and an output indicator. Thecarbon monoxide gas sensor may generate an output electrical currentproportional to a detected concentration of ambient carbon monoxide. Themicrocontroller may have an input that is connected to the carbonmonoxide gas sensor, and an output that is connected to an operationalcontrol of the engine. A deactivation signal generated by themicrocontroller from the output thereof in response to detection of adeactivation condition may be based upon the output electrical currentfrom the carbon monoxide gas sensor matching predefined value andduration thresholds. The deactivation signal may be operative to stopthe engine. The output indicator may be connected to themicrocontroller. A deactivation notification sequence may be generatedon the output indicator in response to the detection of the deactivationcondition.

Another embodiment of the present disclosure is a portable electricalgenerator. There may be an internal combustion engine that includes anelectrical ignition system with an ignition coil. There may also be anengine deactivator that is connected to the electrical ignition systemof the internal combustion engine. The engine deactivator may include acarbon monoxide gas sensor generating an output electrical currentproportional to a detected concentration of ambient carbon monoxide. Theengine deactivator may also include a microcontroller with an inputconnected to the carbon monoxide gas sensor, and an output connected tothe ignition coil. A deactivation signal may be generated by themicrocontroller from the output thereof in response to detection of adeactivation condition, which in turn may be based upon the outputelectrical current from the carbon monoxide gas sensor matchingpredefined value and duration thresholds. The deactivation signal may beoperative to restrict an ignition electrical signal to the ignitioncoil.

Yet another embodiment of this disclosure is a method for deactivatingan engine of a portable electrical generator. The method may include astep of receiving an output electrical current proportional to adetected concentration of ambient carbon monoxide from a carbon monoxidegas sensor. There may also be a step of deriving an ambient carbonmonoxide concentration value from the received output electricalcurrent. Thereafter, the method may include evaluating, on a controller,within a first control loop while the ambient carbon monoxideconcentration value is below a lower threshold, a voltage value from apower supply circuit to the controller. This first control loop may bemaintained while the voltage value corresponds to electrical continuitywith the controller, as well as an active status corresponding to aregular ongoing reception of the output electrical current. The methodmay also include initiating a pre-shutoff loop on the controller. Thismay be in response to the ambient carbon monoxide concentration beingabove an upper threshold. The pre-shutoff loop may include evaluating aplurality of carbon monoxide concentration values over a predeterminedduration. There may also be a step of generating an engine deactivationsignal from the controller in response to the plurality of carbonmonoxide concentration values of the predetermined duration meeting anacceptance criterion. The foregoing method may be implemented as aseries of instructions executable by a data processor and tangiblyembodied in a program storage medium.

The present invention will be best understood by reference to thefollowing detailed description when read in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other advantages and features of the invention will be betterappreciated in view of the following drawings and descriptions in whichlike numbers refer to like parts throughout, and in which:

FIG. 1 is a block diagram showing an exemplary portable generatorincluding a carbon monoxide shutoff module in accordance with oneembodiment of the present disclosure;

FIG. 2 is a block diagram of one embodiment showing additional detailsof the carbon monoxide shutoff module;

FIG. 3 is a flowchart depicting an embodiment of a method fordeactivating an engine of the portable generator; and

FIG. 4 is a flowchart showing additional details of the control loopsimplemented by the carbon monoxide shutoff module.

DETAILED DESCRIPTION

As required, detailed embodiments of the present invention are disclosedherein; however, it is to be understood that the disclosed embodimentsare merely exemplary of the invention, which may be embodied in variousforms. Therefore, specific structural and functional details disclosedherein are not to be interpreted as limiting, but merely as a basis forthe claims and as a representative basis for teaching one skilled in theart to variously employ the present invention in virtually anyappropriately detailed structure. It is further understood that the useof relational terms such as first and second and the like are usedsolely to distinguish one entity from another without necessarilyrequiring or implying any actual such relationship or order between suchentities.

Referring to the block diagram of FIG. 1, one contemplated embodiment ofthe present disclosure is an electrical generator unit 10 withdeactivation features that are, in general, triggered in response tocertain environmental conditions. The present disclosure makes referenceto a “portable” electrical generator unit 10, that is, a generator thatis not permanently installed, and can be moved from one location toanother as the need for electrical power arises. However, this is by wayof example only and not of limitation, and it is to be understood thatembodiments of the present disclosure can be utilized in other contextsand different types and configurations of electrical generators.

As is typical for most conventional implementations, the electricalgenerator unit 10 includes an internal combustion engine 12 that outputsmechanical energy that is then converted to electrical energy with anelectromagnetic generator 14. The engine 12 has an air intake 16 and afuel source 18, the combination of which is mixed and ignited within acylinder to move a reciprocating piston. The combusted gasses are alsooutput from an exhaust 20. The piston, in turn, is understood to bemechanically connected to a rotor of the electromagnetic generator 14.According to various embodiments, the engine 12 may be a four-strokeengine or a two-stroke engine that uses gasoline as its fuel, a dieselengine, or any other suitable engine. Further, simpler engine controlconfigurations using carburetors to meter the fuel and distributors totime the ignition of the fuel may be utilized, as well as more modernfuel injected and computer-controlled ignition. The size/displacement ofthe engine 12 may be varied according to the power ratings of theelectrical generator unit 10. The principles of operation and thenumerous available configurations of the engine 12 are well known in theart, so a detailed consideration of each possible variation that mayfind use in the electrical generator unit 10 will be omitted.

Either the rotor or the stator includes a magnet, while the otherincludes an armature comprised of wire windings. The generated magneticflux is understood to induce a corresponding electrical current in thearmature, which is in electrical communication with an electrical output22. The electromagnetic generator 14 may be an alternator 24 thatoutputs an alternating current (AC) power to the electrical output 22.The electrical power needed to start and continue to operate the engine12 may be provided by a battery 25 that is charged from the alternator24.

Some implementations of the electrical generator unit 10 output the ACsignal directly from the alternator 24. Because the generated currentmust be the same as that which is generated by the power grid, e.g.,120V at 60 Hz, or any other standard, there may be additional controlmodalities to drive the engine 12 at varying speeds to drive thealternator 24 to maintain constant output. In this regard, differentenvironmental conditions that alters the output speed of the enginedriveshaft, that is, the rotor of the alternator, may impact the ACcurrent available from the electrical output 22.

An alternative configuration known as the inverter generator may utilizethe potentially erratic AC power from the alternator 24, and rectifiesand filters that current in a regulator circuit 26 to generate a steadydirect current DC output. The DC current is then utilized to drive aninverter circuit 28 that programmatically generates a precisely timedand clean sinusoidal AC current that does not change in response todiffering mechanical output from the engine 12. The output from theinverter circuit 28 is likewise passed to the electrical output 22.

The higher level control functions for the engine 12 and theelectromagnetic generator 14 may be handled by a controller 30, which isunderstood to be a microcontroller or integrated data processing devicewith input and output capabilities. The microcontroller may beprogrammed with instructions that accept inputs and generates outputs inresponse to the inputs, and perform various steps in accordance withembodiments of the present disclosure. In this regard, themicrocontroller may include memory modules (both read/write capable andread-only varieties). At a basic level, the controller 30 acceptscommands from one or more input devices 32, which may be a simple toggleor pushbutton switch that powers on the electrical generator unit 10, anengine starter button, and the like. Additionally, some embodiments alsocontemplate the use of remote control devices that may communicate overwired signal transmission lines, or wirelessly via radio frequency (RF),infrared, and the like. All such devices are understood to beencompassed within the illustrated feature of the input devices 32.Still further, smartphones, tablets, and other general purposecommunications devices may generate commands that are received by thecontroller 30, and thus may likewise be considered input devices 32.

The controller 30 may also generate information that is presented on oneor more output devices 34. These may include indicators that show theoperational parameters of the electrical generator unit 10, includingvoltmeters (to show the output voltage at the electrical output 22),ammeters (to show instantaneous current output at the electrical output22), fuel low indicators, oil low indicators, power output currentfrequency, and operating timers/counters. The indicators may be assimple as on/off lights that are activated when a fault condition isdetected. The aforementioned remote control devices may also includeindicators, as well as smartphones and tablets that may presenthistorical values alongside the current/instantaneous values.

Various embodiments of the electrical generator unit 10 contemplate theautomatic shutoff of the engine 12 when there has been an accumulationof harmful gasses, including carbon monoxide. As was discussed above,carbon monoxide is odorless, colorless, and non-irritating, but exposureto even moderate concentrations can be harmful. Operating the electricalgenerator unit 10 in enclosed spaces has the potential to increase theconcentration of carbon monoxide to dangerous levels, so the cessationof the internal combustion engine generating this poisonous gas iscontemplated in accordance with the present disclosure. To this end, theelectrical generator unit 10 includes a carbon monoxide shutoff module36. Reference to the shutoff module being related to carbon monoxide,however, is by way of example only, and not of limitation. Theembodiments of the present disclosure may be adapted for shutting downthe electrical generator unit 10 based on concentration levels of otherharmful gasses, in which case, the module may be referred to with suchother gasses. Thus, on a more general level, the carbon monoxide shutoffmodule 36 may also be referenced as an engine deactivator.

As shown in both block diagrams of FIG. 1 and FIG. 2, the carbonmonoxide shutoff module 36 is connected to the engine 12, and in oneembodiment, an ignition coil 38 thereof. It is understood that theair-fuel mixture within the cylinder of the engine 12 is ignited by aspark plug 40. The relatively low voltage from the battery 25 isincreased by the ignition coil 38 so that a spark may be generated bythe spark plug 40. The signal to activate the spark plug 40 mayoriginate from an ignition controller 42, which may be electricallyisolated from the high voltage output of the ignition coil 38. Althoughspecific reference has been made to a battery-powered ignition system,this may be replaced with a magneto ignition system that is activated bythe rotation of the engine.

The carbon monoxide shutoff module 36 may include a carbon monoxide gassensor 44 that generates an output electrical current that isproportional to a detected concentration of ambient carbon monoxide. Inone embodiment, the carbon monoxide gas sensor 44 is an electrochemicalsensor comprised of electrodes that oxidizes the carbon monoxidepresent, with the remaining hydrogen ions migrating into an acidicaqueous electrolyte. The electrons generated at the electrode, whenconnected to an external source, form a small current at the nano-ampere(nA) level. A sensor of this configuration may be the NAP-508 availablefrom Nemoto Sensor Engineering Company Ltd. of Tokyo Japan, though anyother suitable carbon monoxide sensor of alternative types such assemiconductor-type and biomimetic type sensors may be substitutedwithout departing from the present disclosure. An electro-chemicalsensor is understood to be advantageous because of its linear response,fast response and recovery time, high selectivity, humidityindependence, mechanical durability, and requiring no external power.

The carbon monoxide shutoff module 36 includes a microcontroller 46 withan input port that is connected to the carbon monoxide gas sensor 44,and an output that is connected to the ignition coil 38. The input portof the microcontroller 46 may be a single line that is configured toreceive an electrical current, with internal circuitry that measures theanalog current and converts the same to an equivalent digital value. Themicrocontroller may be an Atmel ATtiny861A microcontroller fromMicrochip Technology, Inc. of Chandler, Ariz., though any other suitableintegrated microcontroller device that has sufficient performance, powerconsumption, and input/output capabilities to implement the variousembodiments of the present disclosure may be used. The exemplaryimplementation utilizes a processor clock frequency of 128 kHz, thoughit need not be restricted thereto. One or more of the components of thecarbon monoxide shutoff module 36, e.g., the carbon monoxide gas sensor44 and the microcontroller 46, may be embedded or otherwise disposedwithin an enclosure of the ignition coil 38.

The specific gain response of each carbon monoxide gas sensor 44 mayvary due to manufacturing differences, so the present disclosurecontemplates an initial calibration routine at each startup. During themanufacturing process, an electrically erasable programmable read-onlymemory (EEPROM) connected to the microcontroller 46 may be programmedwith a gain value of the carbon monoxide gas sensor 44 that is beingutilized. By way of example, if the carbon monoxide sensor generates2.865 nA/ppm (parts per million) of carbon monoxide, a value of “2865”may be indicated. This indication may be encoded as a bar code, orprinted on material that is associated with the particular sensor. Whenread, the EEPROM can be programmed with the number “2865,” whichcorresponds to the hexadecimal number B31. A specific memory location inthe EPPROM is programmed with B31, and during the calibration process,the microcontroller 46 may read the same memory location to modify thegain factor to determine the corresponding carbon monoxide concentrationlevels. In an alternative embodiment, the microcontroller 46 mayregularly read the EEPROM location for this data. This embodiment is notunderstood to require a calibration procedure, and the data in theparticular memory location is retrieved whenever needed.

In response to the detected carbon monoxide concentration levels, themicrocontroller 46 may generate a deactivation signal to the ignitioncoil 38. More specifically, a deactivation condition may be detectedbased upon the output electrical current from the carbon monoxide gassensor 44 matching predefined value and duration thresholds. Thedeactivation signal, in turn, may be operative to stop the engine 12 byrestricting the ignition electrical signal to the ignition coil 38. Inthis context, the ignition coil 38 may be referred to as the operationalcontrol. Alternative operational controls that governs the operation ofthe engine 12 may be substituted in accordance with differentembodiments of the present disclosure. Further integration with theelectronic fuel injection (EFI) system and the various componentsthereof is contemplated, including the fuel injector, the fuel pump, thestepper motor for fuel and air delivery, in addition to theaforementioned ignition coil. Furthermore, carbureted engines may alsobe utilized, in which case the operational control may be a fuel cutsolenoid, which may be mounted on the bottom of a float feed carburetor.Various configurations contemplate either a normally open or a normallyclosed setting, such the operational control signal to the fuel cutsolenoid is operative to remove power and close the solenoid withoutpower, or to continuously actuate the solenoid to keep it closed. Whenthe solenoid is closed and fuel supply is stopped, the carburetor may becut off, thereby shutting down the engine within a few seconds. Thespecific value and duration thresholds, and the manner in which thisdata is processed, e.g., the deactivation condition, will be describedin further detail below.

Whenever taking action with respect to the engine 12, themicrocontroller 46 also generates information to one or more outputindicators 50. According to various embodiments of the presentdisclosure, the output indicator 50 is connected to the microcontroller46, and may be remote from the carbon monoxide gas sensor 44, as well asthe microcontroller 46. However, the output indicator 50 is neverthelessdeemed to be part of the carbon monoxide shutoff module 36. Oneembodiment contemplates the use of multi-colored light emitting diodesLEDs as the output indicator 50, though this is by way of example onlyand not of limitation. Contemporaneously with the shutoff of the engine12, the microcontroller 46 generates a deactivation notificationsequence on the output indicator 50. Thus, the deactivation notificationsequence is in response to the detection of the aforementioneddeactivation condition.

As discussed above, the carbon monoxide gas sensor 44 is self-powering,and the microcontroller 46 is powered by an electrical current tappedfrom the ignition coil 38. More particularly, the carbon monoxideshutoff module 36 includes a power supply capacitor 48 that suppliespower to the microcontroller 46 after the engine 12 has been shut off,and there is no longer power from the ignition coil 38. In this regard,a battery that would otherwise be required to power the microcontroller46 can be eliminated. Along the same lines, a battery that may be neededto power the output indicator 50 may also be eliminated, and powered fora limited time from the power supply capacitor 48.

Some embodiments of the electrical generator unit 10 include a remotestarter, which may be a combined input device 32 and output device 34 inthe context of the block diagram of FIG. 1. Under some circumstances,the user may restart the electrical generator unit 10 after a shutoffevent, provided that the unsafe condition that necessitated it in thefirst place passes. The remote starter may be in communication witheither the controller 30 of the electrical generator unit 10, orspecifically the microcontroller 46 of the carbon monoxide shutoffmodule 36. The remote starter is understood to generate a remote restartcommand in response to a user input, and may be conditionally operativeto restart the engine 12 because the carbon monoxide concentrationlevels is checked to confirm safe levels before restarting. Under otherconditions that are deemed to be unsafe, the restart may be disabled.Further details on the methodology of allowing or disallowing restartswill be considered below.

The present disclosure contemplates various embodiments of methods fordeactivating the engine 12 of the electrical generator unit 10. Withreference to the flowchart of FIG. 3, one method begins with a step 100of receiving the output electrical current of the carbon monoxide gassensor 44. As discussed above, this electrical current is proportionalto the detected concentration of ambient carbon monoxide. Then, also asconsidered previously, there is a step 102 of deriving an ambient carbonmonoxide concentration value from the output electrical current. Withthe carbon monoxide gas sensor 44 generating increasing levels ofcurrent in response to carbon monoxide concentration levels, themeasured current can be computed to a specific concentration value.

The aforementioned steps 100 and 102 of receiving the output of thecarbon monoxide gas sensor 44 and deriving the carbon monoxideconcentration level continues throughout. In a first control loop perillustrated step 104, the microcontroller 46 may evaluate the carbonmonoxide concentration value, and so long as it is below a lowerthreshold, further evaluate a voltage value from a power supply circuitto the microcontroller 46. The power supply circuit in one embodiment isunderstood to be the connection between the power supply capacitor 48and the ignition coil 38, as well as components connected thereto thatserve a power supply function. So long as the voltage value is thatwhich corresponds to an active status in which there is a regularongoing reception of the output electrical current, e.g., the carbonmonoxide shutoff module 36 has not been disconnected for any reason, andthe other aforementioned conditions are maintained, the first controlloop continues. However, it is also possible to power the carbonmonoxide shutoff module 36 with a battery that is utilized as part ofthe engine ignition system, or the additional winding in a magneto-basedimplementation.

According to next step 106, the microcontroller 46 initiates apre-shutoff loop if or once the carbon monoxide concentration valueexceeds an upper threshold. The pre-shutoff loop involves an evaluationof a plurality of carbon monoxide concentration values over apredetermined duration. The loop exiting conditions or acceptancecriterion may be, for example, if the average of the carbon monoxideconcentration value over a certain timespan exceeds a limit. Once thispre-shutoff loop is exited, execution continues to a step 108 ofgenerating the engine deactivation signal. Stated alternatively, thestep 108 takes place when a plurality of carbon monoxide concentrationvalues of the predetermined duration meet an acceptance criterion.

There may also be a substantially contemporaneous step 110 of generatingan engine deactivation indicator output on the output indicator 50, orother remove visual indication device. As utilized herein, substantiallycontemporaneous is understood to mean around the same time. Themicrocontroller 46 may execute the instructions generating the enginedeactivation signal before or after generating the corresponding output,but from the perception of the user viewing the electrical generatorunit 10 and the output indicator 50, it may appear to occursimultaneously. There may also be a delay between the engine 12deactivating and the output indicator 50 illuminating. However, so longas the user has the perception that the indicator in general accuratelyreflects the current status of the electrical generator unit 10, it isto be considered substantially contemporaneous.

Additional details of the process and methodology implemented by thecarbon monoxide shutoff module 36 will now be considered with referenceto the flowchart of FIG. 4. Prior to beginning a main control loop 1000,there is an initialization step 900 in which the aforementioned EEPROMvalues are read to retrieve the sensor gain value. A short time delayof, for example, four seconds, is also introduced to stabilize thecarbon monoxide gas sensor 44. Optionally, though preferably, a watchdogtimer is also set to allow for a graceful exit in case of a stuck loop.Additionally, the presence of a remote and/or local output indicator 50is determined, with all subsequent indicator outputs being directed tothe one that is available.

Upon entering the main control loop 1000, there are a series ofevaluations of the derived carbon monoxide concentration value, as wellas other signals and voltages that were generally described above. In afirst decision branch 1002, the carbon monoxide concentration value isdetermined whether it is greater than a first lower concentration limit.If not, the process enters a second decision branch 1004 to evaluatewhether the power supply reference voltage is greater than 0.75V. Thisevaluation may be made once every minute. In one embodiment the powersupply reference voltage as determined by the microcontroller 46, PSREF,is given as an integer, so the evaluation is whether this is less thanor greater than a second lower concentration limit value. If less thanthe second lower concentration limit value, it is assumed in a step 1006that the power supply wire to the carbon monoxide shutoff module 36 wascut or tampered with, and the system proceeds to shut off the electricalgenerator unit 10 in accordance with a step 1008. There is contemplatedto be no restrictions as to how quickly this takes place. Additionally,no outputs are generated to the output indicators 50, and no data issaved to memory.

If, on the other hand, the PSREF is greater than the second lowerconcentration limit value 75, then a self-monitoring system determineswhether the carbon monoxide shutoff module 36 is live or dead in a step1010. More particularly, the port of the microcontroller 46 to which thecarbon monoxide gas sensor 44 is connected is driven high for an initialstate, then pulsed logic low for an exemplary 70 milliseconds. With theanalog-to-digital converter of the microcontroller 46 thereafterderiving the voltage on the sensor input port, the carbon monoxide levelvalue (COLEV) is understood to change from 1 volt to the high level, andthe ADCH (analog-to-digital converter high port) rises to may rise ashigh as 50. If the ADCH value is greater than 10 per a third decisionbranch 1012, the test is passed, and the process returns to the maincontrol loop 1000. However, if lower than 10, the carbon monoxide gassensor 44 is assumed to be dead per step 1014, and begins the shutoffprocedure.

As mentioned above, different colors of output indicators 50 may beutilized. In an exemplary embodiment, a yellow color LED may be used toindicate a system fault event. Such yellow LED may be activated fortwenty seconds, whether it be a remote or local output indicator 50.Thereafter, the LED may be blinked for 400 milliseconds on, and 1600milliseconds off. A sensor failure event is recorded in memory, and theelectrical generator unit 10 will be locked out for twenty seconds.These values are presented by way of example only and not of limitation,and may depend on the size of the power supply capacitor 48. A largercapacitance and charge-holding capability may lengthen the time in whichthe output indicator 50 can be illuminated, while a smaller capacitancemay reduce the time.

Remotely restarting the electrical generator unit 10 may be allowed ordisallowed as desirable. So long as no restart command is received asevaluated in a fourth decision branch 1016, the system keeps the yellowLED blinking for at least 5 minutes per step 1018. The blinking isunderstood to stop when the power supply capacitor 48 has no moreenergy. If a restart command is received as evaluated in the fourthdecision branch 1016, the process returns to the main control loop 1000.

Returning to the first decision branch 1002, if the carbon monoxideconcentration value is determined to be greater than a first lowerconcentration limit value, a fifth decision branch 1020 evaluateswhether the carbon monoxide concentration value is between a first lowerconcentration limit and an upper concentration limit. During this time,the aforementioned live or dead check may be suspended. If between thefirst lower concentration limit and the upper concentration limit, thecarbon monoxide concentration value continues to be evaluated, again inthe first decision branch 1002. Otherwise, the carbon monoxideconcentration value is evaluated whether it is greater than the upperconcentration limit in a sixth decision branch 1022. If no, the carbonmonoxide concentration value is evaluated in the fifth decision branch1020, whether it is between the first lower concentration limit and theupper concentration limit.

When the carbon monoxide concentration value is greater than the upperconcentration limit, the process continues to a seventh decision branch1024 to determine whether certain acceptance criteria are met. This isunderstood to correspond to the aforementioned pre-shutoff loop 106,where a rolling average carbon monoxide concentration value for a setduration is evaluated. For example, one acceptance criteria is a secondupper concentration limit of carbon monoxide concentration that isdetected at least two consecutive readings. Another acceptance criteriais a rolling average of an upper concentration limit of carbon monoxideconcentration readings over 5 minutes. In either case, the electricalgenerator unit 10 is shut off in accordance with step 1026, and theoutput indicator 50 is illuminated. The specific values of theconcentration limits to select for the foregoing procedure may bevaried, and are within the purview of those having ordinary skill in theart.

Due to the greater severity of the cause of this shut off, a red LED isenvisioned. Two of the red LEDs may be turned solidly on for twentyseconds, then blinked for 400 milliseconds on, and 1600 millisecondsoff. Again, the electrical generator unit 10 is locked out for twentyseconds, and the particular event that led to the shutoff is recorded inmemory. Remote restart is also disabled, and the electrical generatorunit 10 can only be restarted locally. If a local restart command isreceived as evaluated in an eighth decision branch 1028, the processreturns to the main control loop 1000 following the shutoff eventnotification in a step 1030.

As the microcontroller 46 executes the instructions corresponding to theforegoing procedure, various data is recorded and stored. Additionaldiagnostic information such as the number of shutdowns, the type of eachof those shutdowns, the total run-time, and the like may be stored inthe EEPROM. These values may be retrieved by an externally connecteddiagnostic tool and/or viewed on a general-purpose computer systemconfigured for reading and presenting such data. The specifics oflogging diagnostic data is deemed to be within the purview of one havingordinary skill in the art, so no additional details thereof will beconsidered herein. The particulars shown herein are by way of exampleand for purposes of illustrative discussion of the embodiments of thepresent disclosure only and are presented in the cause of providing whatis believed to be the most useful and readily understood description ofthe principles and conceptual aspects. In this regard, no attempt ismade to show details of the present invention with more particularitythan is necessary, the description taken with the drawings makingapparent to those skilled in the art how the several forms of thepresent invention may be embodied in practice.

What is claimed is:
 1. A carbon monoxide shutoff system for an engine ofa portable electrical generator, the system comprising: a carbonmonoxide gas sensor generating an output electrical current proportionalto a detected concentration of ambient carbon monoxide; amicrocontroller with an input connected to the carbon monoxide gassensor, and an output connected to an operational control of the engine,a deactivation signal generated by the microcontroller from the outputthereof in response to detection of a deactivation condition based uponthe output electrical current from the carbon monoxide gas sensormatching predefined value and duration thresholds, the deactivationsignal being operative to stop the engine; and an output indicatorconnected to the microcontroller, a deactivation notification sequencebeing generated on the output indicator in response to the detection ofthe deactivation condition.
 2. The carbon monoxide shutoff system ofclaim 1, wherein the operational control of the engine is an ignitioncoil, the deactivation signal being operative to cut an ignitionelectrical signal to the ignition coil.
 3. The carbon monoxide shutoffsystem of claim 2, wherein the microcontroller and the carbon monoxidegas sensor are embedded within an enclosure of the ignition coil.
 4. Thecarbon monoxide shutoff system of claim 2, wherein electrical power tothe microcontroller and the output indicator is generated by thegenerator solely during active operation thereof.
 5. The carbon monoxideshutoff system of claim 4, further comprising a power supply capacitorconnected to a power supply, the power supply capacitor being charged bythe power supply.
 6. The carbon monoxide shutoff system of claim 5,wherein the power supply capacitor provides the electrical power to themicrocontroller and the output indicator after the engine is deactivatedand the ignition electrical signal is absent.
 7. The carbon monoxideshutoff system of claim 1, wherein the operational control of the engineis a fuel injector, the deactivation signal being operative todeactivate the fuel injector.
 8. The carbon monoxide shutoff system ofclaim 1, wherein the operational control of the engine is a fuel pump,the deactivation signal being operative to deactivate the fuel pump. 9.The carbon monoxide shutoff system of claim 1, wherein the operationalcontrol of the engine is a stepper motor connected to a fuel deliveryvalve, the deactivation signal being operative to drive the motor to aclosed state of the fuel delivery valve.
 10. The carbon monoxide shutoffsystem of claim 1, wherein the operational control is a carburetor fuelcut solenoid, the deactivation signal being operative to close thecarburetor fuel cut solenoid.
 11. The carbon monoxide shutoff system ofclaim 1, wherein the deactivation signal is transmitted to an electronicfuel injection engine control unit.
 12. The carbon monoxide shutoffsystem of claim 1, wherein the output indicator is one or more lightemitting diodes.
 13. The carbon monoxide shutoff system of claim 1,further comprising a remote starter in communication with themicrocontroller, a remote restart command being generated in response toan input received on the remote starter, the remote restart commandbeing conditionally operative to restart the engine.
 14. The carbonmonoxide shutoff system of claim 13, wherein the restart of the enginebased upon the remote restart command is disabled under a predefinedcondition evaluated by the microcontroller.
 15. A portable electricalgenerator, comprising: an internal combustion engine includingelectrical ignition system with an ignition coil; an engine deactivatorconnected to the electrical ignition system of the internal combustionengine, the engine deactivator including: a carbon monoxide gas sensorgenerating an output electrical current proportional to a detectedconcentration of ambient carbon monoxide; and a microcontroller with aninput connected to the carbon monoxide gas sensor, and an outputconnected to the ignition coil, a deactivation signal generated by themicrocontroller from the output thereof in response to detection of adeactivation condition based upon the output electrical current from thecarbon monoxide gas sensor matching predefined value and durationthresholds, the deactivation signal being operative to restrict anignition electrical signal to the ignition coil.
 16. The portableelectrical generator of claim 15, further comprising an output indicatorconnected to the microcontroller and remote from the engine deactivator,a deactivation notification sequence being generated on the outputindicator in response to the detection of the deactivation condition.17. The portable electrical generator of claim 16, wherein the outputindicator is one or more light emitting diodes.
 18. The portableelectrical generator of claim 15, wherein electrical power to themicrocontroller and the output indicator is generated by the enginesolely during active operation thereof.
 19. The portable electricalgenerator of claim 18, further comprising a power supply capacitorconnected to the power supply coil, the power supply capacitor beingcharged by the power supply electrical signal.
 20. The portableelectrical generator of claim 19, wherein the power supply capacitorprovides the electrical power to the engine deactivator after the engineis deactivated and the ignition electrical signal is absent.
 21. Theportable electrical generator of claim 15, further comprising a remotestarter in communication with the engine deactivator, a remote restartcommand being generated in response to an input received on the remotestarter, the remote restart command being conditionally operative torestart the engine.
 22. A method for deactivating an engine of aportable electrical generator comprising the steps of: receiving from acarbon monoxide gas sensor an output electrical current proportional toa detected concentration of ambient carbon monoxide; deriving an ambientcarbon monoxide concentration value from the received output electricalcurrent; evaluating, on a controller, within a first control loop whilethe ambient carbon monoxide concentration value is below a lowerthreshold, a voltage value from a power supply circuit to the controllercorresponding to electrical continuity therewith and an active statuscorresponding to a regular ongoing reception of the output electricalcurrent; initiating, on the controller, a pre-shutoff loop in responseto the ambient carbon monoxide concentration being above an upperthreshold, the pre-shutoff loop including evaluating a plurality ofcarbon monoxide concentration values over a predetermined duration; andgenerating an engine deactivation signal from the controller in responseto the plurality of carbon monoxide concentration values of thepredetermined duration meeting an acceptance criterion.
 23. The methodof claim 22, wherein the engine deactivation signal restricts anignition electrical signal to an ignition coil driving the engine. 24.The method of claim 23, wherein electrical power to the controller isgenerated by the generator solely during active operation thereof, theelectrical power charging a power supply capacitor connected to thepower supply and to the controller.
 25. The method of claim 22, furthercomprising: generating an engine deactivation indicator output on aremote visual indication device in response to the plurality of carbonmonoxide concentration values of the predetermined duration meeting theacceptance criterion.